The invention is based on a blower according to the preamble to claim 1.
In reciprocating piston engines with three-way catalytic converters, particularly during a cold start, fresh air is blown into the exhaust system by means of secondary blowers in order to initiate an exothermic afteroxidation of uncombusted carbon compounds. The combustion process reduces the amounts of carbon monoxide and hydrocarbons in the exhaust and it is possible to rapidly bring the catalytic converter to a favorable operating temperature.
The blowers produce a large amount of noise, particularly when high flow speeds and an intense pressure increase are produced with high speeds. In order to reduce the noise, the fresh air can be aspirated through an air filter of the reciprocating piston engine. Additional lines are required for this, though, which involves higher costs. If the fresh air is aspirated from the outside air through an unsealed opening, then as a rule separate sound dampers are used in the intake region.
DE 42 05 489 A1 has disclosed a blower whose sound damper is mounted on the blower as a separate component. It has a housing cup with a flat cup bottom, a cup wall, and a housing cover that closes the cup opening. An air inlet opening in the cup wall and an air outlet conduit with a central opening in the housing cover are connected by means of a spiral conduit which is constituted by an insulating insert made of open-pored sound absorption material. In the axial direction of the sound damper, the conduit reaches from the cup bottom to the housing cover and is axially defined by these parts. The sound damper is built into an intake line of the blower by means of a connection fitting. Sound dampers of this kind can also be used for other purposes, in particular in blowers for ventilation systems of motor vehicles.
DE 196 31 664.2 has disclosed a blower with a sound damper, which has a housing with an air inlet opening on the circumference and an air outlet conduit with an air outlet opening at one end. The air outlet opening is disposed in the center or off center and is connected to an inlet opening in an end wall of the blower housing. The housing of the sound damper is fastened to the blower housing and is open in the direction of the blower, wherein the end wall serves as a common dividing wall between the blower housing and the housing of the sound damper, which has no housing cover. One layer of the sound absorption material rests directly against the blower housing. Thus the sound damper does not require a housing cover and the sound radiation of the blower is reduced.
In order to be able to mount an impeller of the blower on a drive shaft, the blower housing is divided in a plain lateral to the drive shaft. The two parts ate screw connected to each other. To that end, the parts of the blower housing have cylindrical fitting surfaces on the circumference. Bearing surfaces and fastening elements are likewise required in order to fasten the sound damper to the blower.
According to the invention, the housing of the sound damper constitutes the end wall of the blower housing and defines the chamber for the impeller. Before installation of the sound damper, the impeller can be mounted from the open end. Then, the opening of the blower housing is closed by the housing of the sound damper. This consequently replaces a part of the blower housing, thus reducing the number of parts, assembly- and fitting surfaces, and connecting means. Assembly is also simplified. In addition, the blower is shorter in the axial direction and the structure as a whole is lighter in weight.
In a suitable fashion, on its side oriented toward the blower housing, the housing of the sound damper has a collar which is inserted into a recess in the blower housing. This centers the two parts in relation to each other, wherein the sound damper can be rotated in relation to the blower around the drive axis so that the position of its air inlet opening can be easily adapted to the installation conditions in the vehicle. Advantageously, the housing of the sound damper has an additional collar formed onto it which overlaps the blower housing circumferentially. Consequently, the blower is sealed in this region so that no outside air can get into the blower and no sound can escape to the outside.
Since the sound damper according to the invention covers the entire end face of the blower, the sound radiating surface area of the blower housing is sharply reduced. In addition, the large circumference of the sound damper allows for longer conduit which likewise has a positive effect on the sound damping.
The housing of the sound damper is fastened to the blower housing by means of retaining clips, which simplifies assembly and disassembly and facilitates the alignment of the sound damper. In addition, the blower housing can be manufactured more inexpensively since fixing devices are no longer required for the fastening elements.
According to one embodiment of the invention, oriented toward the impeller, the sound damper has a disk which is preferably made of sheet metal and is clamped between the sound damper and the blower housing, thus constituting the common dividing wall. It is likewise inserted into the end face recess on the blower housing and is centered along the circumference. The sheet metal disk can be easily modified in thickness and shape, as a result of which the sound radiation spectrum can be matched to the installation conditions. Simultaneously, the insulating action is improved by the mass of the material.
In the center, the sheet metal disk has an inlet opening with a collar formed onto it which protrudes into the chamber for the impeller. The air flows into the chamber with the impeller through this inlet opening. The diameter of the inlet opening and/or the radius at the formed collar can be adapted to the optimal operating point of the blower in a simple way.